Process for making foamlike mass of metal



Patented Jan. 20, 1948 .PROCESE .FQR MAKING FOAMLIKE MASS OF METALBenjamin Sosnick, San Francisco, Calif.

No Drjawing. Application May s, 1943, Serial No. 486,209

r Glaims. (or. 75-20 1 This invention relates to'asponge metal and theprocess of making it.

The name, sponge metal/is used herein to designate a metal productin-any'desiredshape and form in which the metal-contains a plurality ofclosely adjacent spaces or voids-of partial vacuum or fluid. The metalstructurally resembles a-solidified'foamy mass of metal.

One of the objects of'the invention isthe process of making the spongemetal from a'mixture of As a concrete example, assuming aluminum and-1nercury are used, these maybe mixed in the proportion of 90 parts .ofaluminum to parts of mercury, and. are melted in a closed chamber or.under conditions preventing escape of the mercury vapor. Theproportions are, of course,

' greatly (dependent uponithe capacity of the enclosure to produce-adesired vapor pressure, that metals, compounds, alloys,'elements, orminerals,

and the resultant product therefrom.

Another object is the product of my process of fmaking the sponge metal,and which product is a solidified, foamy'mass of metal having extremelightness in proportion to the volumetric mass of 'the metal and beingstructurally resistant to "shock and strain proportional-to thenormalresistanoe of ordinary metal or the same kind, while possessing greaterresiliency to impact not found where the mass of metal is solid.

v Briefly described, the sponge metal of this invention maybe cast,fashioned, processed; or out to the desired shape, such as blocks,sheets, plates, tubing, or in whatever formis desired. As the 'cells inthe metal are not intercommunicating, it

possesses heat insulation properties and the metal may obviously be maderesistant to oxidization, either by its inherent nature or by treatmentof its exposed surface. Also the metal has sound and vibration absorbingproperties.

In general, the process of making the metal comprises heating thedesired metal, mixture of metals, compounds, alloys, or other'minerals,etc., to a temperature between the melting point thereof at atmosphericpressure and a temperature sufficient to produce a, vapor pressure ofvolatile material in the mixture, and under conditions where thevolatile portion or portions are held in the molten mass against escapetherefrom. The molten mass is then released into a lower pressure spaceresulting in'the formation of a froth or mass of metallic, gas filledbubbles, which, after cooling will constitute the sponge metal.

As examples of mixtures that are suitable for forming sponge metal, oneor more of the following combinations may be used:

In carrying out this process, any conventional apparatus may be employedcapable of withstanding the necessary heat and pressure, it beingunderstood that the volatile portion of the material treated isprevented-from escape so as to'produce the desired vapor pressure.

foamy or sponge-like.

is, the less vapor pressure space the less mercury is required, and thegreater the space the more is needed.

At atmospheric pressure, the aluminum should melt at about1658 .C. andas the boiling pointrof mercury is about 357 C. it will be seen that avapor pressure due to the yolatilizing of the mercury may .be increased:to the point where the -mercury in themixture is stabilized or is notvaporized unless there isa reduction in pressure. When this condition isreached and the pressure is released, which may be "by withdrawing themolten mass from the high pressure chamberto 'alow pressure space, therewillbe a volatiliaing of the mercury in the mass causing it ;to becomeUpon cooling a sponge metal will-result.

Where iron, aluminum and .zinc are used, the "relative rproportions'ofaluminum-to iron m y be from about 1% iron-to aluminum by weight,

or from 90% to 10% aluminum, and from 1% to 20% of zinc relative to'theentire mass will sup- :ply the desired-amount .of zinc for supplying thevapor. A .higher temperature will normally re- "sult in less zinc beingrequired.

In all instances in compositions of diiierent metals their meltingpoints will vary from that of the respective metals, hence exact meltingpoint temperatures cannot be given.

In zinc alloys the zinc in the alloy will be suftlcient to produce thenecessary gas, and where mercury is used, from 1% to 10% by weight ofthe entire mass is generally adequate, and Where no amalgam is formed,there will be some free mercury in the cells in the sponge metal, butthe empty spaces will nevertheless beformed.

Iron alone with 1% to 20% zinc, or magnesium and iron with 1 to 20%magnesium, or magnesium and zinc may be used to form the metal.

As an example of a mineral and a metal, gold and mercuric oxide meltedtogether in aconfined space will produce sponge metal.

The pressure produced will vary in Proportion to temperature,composition andsolubility, but as a general principal in all instancesthe heating is to the point where vapor pressure of volatile material ormaterials is above the pressure of the space into which the moltenmaterial is to be released, or a relativelyrapid lowering of pressure inthe space in which the material is melted is the equivalent if themolten material is not drawn from the space in which it is melted.

The abcve principle being understood, it is, of

8 course, obvious that the invention is not restricted to exact metalsdisclosed, but to any metallic mixture, compound, alloy, etc., in whicha metal or mineral is incorporated therein that has a relatively lowerboiling point than the main body of the mass so as to produce the vaporpressure in the molten mass suificient to create the conditions in whicha release of the vapor pressure will result in subsequent volatilizingof the said metal or mineral in the mass to produce the cellularstructure when the mass is cooled in the low pressure space or area.

While earlier herein the statement was made that the cells in the spongemetal were not intercommunicating, this statement is to be takengenerally, since some intercommunication between certain cells cannot beavoided.

Having described my invention, I claim:

1. The process of making a metal containing substantially throughout itsbody completely enclosed voids that comprises melting the metal belowits boiling point at atmospheric pressure out of contact with theatmosphere in the presence of material relatively volatile with respectto the treated metal at a temperature above the boiling point of thelatter at atmospheric pressure, and under pressure sufiicient tosubstantially raise the boiling point of the said latter material,thereafter reducing the said latter pressure to below the boiling pointpressure of said latter material, and thereafter cooling to produce thesolidified metal containing the enclosed voids.

2. The process of making a metal containing substantially throughout itsbody completely enclosed spaces that comprises melting the metal belowits boiling point at atmospheric pressure out of contact with theatmosphere in the presence of material relatively volatile with respectto the treated metal at a temperature above the boiling point of thelatter at atmospheric pressure, and under pressure sufficient to preventthe escape of the relatively volatile material therefrom, thereafterreducing the said latter pressure to below the boiling point pressure ofsaid relatively volatile material, and thereafter cooling to produce thesolidified metal containing the enclosed spaces.

3. The process of making a metal containing substantially throughout itsbody closely adjacent completely enclosed spaces that comprises ;meltingthe metal below its boiling point at atmospheric pressure out of contactwith the at- .mosphere in the presence of material relatively volatilewith respect to the treated metal at a temperature above the boilingpoint of the latter at atmospheric pressure, and under pressuresufiicient to substantially raise the boiling point of the saidrelatively volatile material, thereafter reducing the said latterpressure to below the boiling point pressure of said relatively volatilematerial, and thereafter cooling to produce the solidified metalcontaining the enclosed spaces.

4. The process of making a metal containing substantially throughout itsbody closely adjacent completely enclosed non-communicating spaces thatcomprises melting the metal below its boiling point at atmosphericpressure out of contact with the atmosphere in the presence of anothermetal relatively volatile with respect to the treated metal at atemperature above the boiling point of the latter at atmosphericpressure, and under pressure sufficient to substantially raise theboiling point of the said relatively volatile metal, thereafter reducingthe said latter pressure to below the boiling point pressure of saidrelatively volatile metal, and thereafter cooling to produce thesolidified metal containing the enclosed spaces.

5. The process of making a solidified foamlike mass of metal containingsubstantially throughout its body closely adjacent completely enclosednon-communicating spaces that comprises melting the metal below itsboiling point at atmospheric pressure out of contact with the atmospherein the presence of another metal relatively volatile with respect to thetreated metal at a temperature above the boiling point of the latter atatmospheric pressure, and under pressure sufficient to substantiallyraise the boiling point of the said relatively volatile metal,thereafter releasing into a lower pressure space the molten metal toform a foam-like mass of metal, and thereafter cooling said mass toproduce the solidified metallic mass containing the enclosed spaces.

6. The process of making a solidified foamlike mass of metal containingsubstantially throughout its body closely adjacent non-communicatingcompletely enclosed spaces which comprises mixing molten metal at atemperature below its boiling point at atmospheric pressure out ofcontact with the atmosphere with another metal relatively volatile withrespect to the treated metal, and under pressure sufficient tosubstantially raise the boiling point of the said relatively volatilemetal, thereafter releasing into a lower pressure space the molten metalto form a foam-like mass of metal. and thereafter cooling said mass toproduce the solidified foam-like metallic mass.

'7. The process of making a solidified foam-like mass of metalcontaining substantially throughout its body closely adjacentnon-communicating completely enclosed spaces which comprises mixingmolten metal at a temperature below its boiling point at atmosphericpressure out of contact with the atmosphere with another materialrelatively volatile with respect to the treated metal, and underpressure sufficient to substantially raise the boiling point of the saidrelatively volatile material, thereafter releasing into a lower pressurespace the molten metal to form a foamlike mass of metal, and thereaftercooling said mass to produce the solidified foam-like metallic mass.

BENJAMIN SOSNICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Principles of Powder Metallurgy,by W. D. Jones, published by Edward Arnold & Co., London, 1937, pages133, 134 and 135.

The Making, Shaping and Treating of Steel, by Camp and Francis,published by the Carnegie Illinois Steel Co. of Pittsburgh, Pa., pages65% and 655.

